The xDSL is a high-speed data transmission technology for transmitting data in telephone twisted-pair cables. With the increase of a frequency band used by the xDSL, a problem of high frequency crosstalk becomes more prominent. When multiple subscribers need to launch an xDSL service in a bundle of cables, due to the crosstalk problem, rates of some lines become lower, performance of them becomes unstable, and sometimes the service even cannot be launched. As a result, a Digital Subscriber Line Access Multiplexer (DSLAM) has a low line activation rate. Multiple twisted-pair cables are present on the cables of the subscribers, and various services may run on each twisted-pair cable. When various types of xDSLs work simultaneously, crosstalk is generated between the lines, and the performance of some lines drops sharply due to the crosstalk problem. When the lines are longer, lines of some twisted-pair cables cannot launch any forms of DSL services at all.
In the prior art, joint transmission and reception are performed by using a precoder or canceller at a DSLAM end, and crosstalk interference is cancelled by using a signal processing method, so that crosstalk in each path of signal is eventually eliminated.
In a training procedure, the training time of the precoder or canceller is always a fixed and high value, so that the precoder or canceller has great interference on adjacent subscribers during a training procedure, or even leads to call drops of other subscribers when the interference is serious.